The present invention relates to a system for closing a pivoting thrust reverser door pivotally attached to a jet engine cowling, more particularly such a system which grips the thrust reverser door when it is adjacent to its closed, forward thrust position and exerts a force on a forward portion of the door to securely close and lock the thrust reverser door in the forward thrust position.
Pivoting doors for aircraft thrust reversers are well-known in the art and are typically incorporated into a jet engine cowling so as to pivot about a generally transverse axis between a closed, forward thrust position and an open, reverse thrust position in which the door opens a reverse thrust opening in the cowling and redirects at least a portion of the gases passing through a duct bounded by the cowling outwardly through the reverse thrust opening. The thrust reverser door is driven between the closed, forward thrust position and the open, reverse thrust position by an actuator attached to the door and to the structure of the engine cowling. Locks are utilized to keep the thrust reverser door in the closed, forward thrust position to prevent inadvertent deployment of the door to the reverse thrust position. Sealing is achieved by interposing one or more elastomer seals between the engine cowling structure and the thrust reverser door.
The actuator is typically a linear actuator and is pivotally attached to the cowling structure forwardly of the reverse thrust opening so as to swivel about its attachment point as the thrust reverser door moves between the closed and opened positions. The actuator is typically a linear actuator which exerts a force on the door along a central longitudinal axis of the linear actuator. The position of the actuator within the wall thickness of the jet engine cowling causes the linear force exerted on the door by the linear actuator to move closer to the pivot axis of the door as the thrust reverser door approaches the closed, forward thrust position, thereby reducing the torque exerted on the door by the linear actuator force. Under some aircraft operating conditions, the pivoting torque exerted on the thrust reverser door by the linear actuator may become insufficient to fully close the thrust reverser door in a rapid fashion. Also, under such conditions, the forces applied by the linear actuator on the jet engine cowling structure and the thrust reverser door may be of such magnitude to cause deformation of the cowling structure and the door.
The closing of the thrust reverser door is accompanied by compression of the elastomeric seals between the thrust reverser door and the cowling structure, thereby necessitating an additional torque applied to the thrust reverser door when approaching its fully closed condition in order to adequately compress the elastomeric seals. The above-described phenomenon is compounded by the need to "over-retract" the thrust reverser door, that is, to push it into the reverse thrust opening of the jet engine cowling more than ideally necessary and to compress the elastomeric seals in order to be able to lock the thrust reverser door despite any deformations in the cowling and/or the thrust reverser door and in order to minimize the force required to move the locking device between its locked and unlocked position. When fully locked in the fully closed position, the outer surface of the thrust reverser door will align itself with the outer surface of the engine cowling to provide an aerodynamically smooth outer surface for the cowling structure.
In order to resolve the known problems, solutions are available, but none completely resolve all of the problems. First, the force exerted by the linear actuators and the mechanical strengths of the cowling structure and the thrust reverser doors may be increased. However, this increases the weight and bulk of the thrust reverser structure causing higher aircraft fuel consumption and lower useful load capable of being carried by the Aircraft. Secondly, the operation of the gas turbine engine may be restricted during the thrust reverser door closure in order to lower the forces acting on the thrust reverser doors and thereby enabling the known linear actuators to reliably fully close the thrust reverser doors. However, such restriction may entail grave difficulties in actual aircraft practice. Such difficulties may arise when the aircraft is landing and the thrust reversers are in their reverse thrust positions and an unexpected obstacle appears in front of the aircraft. If the gas turbine engine operation is restricted, the pilot will be unable to apply the full power of the engine to close the thrust reverser doors to enable the aircraft to take off and avoid the obstacle without encountering a delay of several seconds. Thus, a need exists for a system for reliably closing the thrust reverser door without increasing the weight of the thrust reverser structure and without requiring restrictions of the gas turbine engine operation.